In recent years, multilayer ceramic electronic components are mounted in various electronic devices, and ceramic materials such as dielectric porcelain compositions used for the multilayer ceramic electronic components are also being actively studied and developed.
This type of dielectric porcelain composition has ferroelectricity disappearing when its Curie temperature Tc is exceeded, and accordingly, to maintain ferroelectricity at higher temperature, it is desired to have a high Curie temperature.
For example, Patent Document 1 proposes a ferroelectric ceramic composition which comprises lead titanate, calcium titanate, and antimony titanate as basic components and has a basic composition represented by the chemical formula (1−x−y) PbTiO3-xCaTiO3-ySb2/3TiO3, where x=1.0 to 35 mol % and y=1.0 to 30 mol %, and in the above chemical formula, Ti is substituted with Mn by 0.5 to 5 mol %.
Patent Document 1 attempts to obtain a ferroelectric ceramic composition having a high Curie temperature of 200° C. or higher and hence being satisfactorily heat resistant by containing a prescribed amount of Mn in a form of substituting a portion of Ti in a component system having PbTiO3, CaTiO3, and Sb2/3TiO3 as basic components.
Furthermore, Non-Patent Document 1 reports local-structure origins of the sustained Curie temperature in (Ba,Ca)TiO3 ferroelectrics.
Non-patent document 1 describes that BaTiO3 has a Curie temperature Tc of about 400 K (about 127° C.), and while the Curie temperature Tc tends to increase by substituting a portion of Ba with Ca, there exists a Ca content for which the Curie temperature Tc peaks, and when a portion of Ba is substituted with a prescribed amount of Ca or more, the Curie temperature Tc decreases. Specifically, when Ca has a molar ratio x of 0.2 to a total of Ba and Ca, the Curie temperature Tc will be about 410 K (about 137° C.), which is higher than that of BaTiO3, whereas when Ca has a molar ratio x increased to 0.3, the Curie temperature Tc will be about 375 K (about 102° C.), which is lower than that of BaTiO3.
Patent Document 1: Japanese Patent Laying-Open No. 9-183652 (see claim 1 and table 1)
Non-Patent Document 1: I. Levin, et al., “Local-structure origins of the sustained Curie temperature in (Ba,Ca)TiO3 ferroelectrics,” Applied Physics Letters, 102, 162906 (2013).